JP2008157758A - Contact probe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a contact probe capable of preventing metal powder produced due to the abrasion of the inside surface of a barrel from accumulating in the clearance between a plunger and the barrel, or hampering the sliding of the plunger. <P>SOLUTION: The contact probe is provided with the cylindrical barrel 1, a coil spring 2 which the barrel 1 has built-in, and the plunger 3 which is urged by the coil spring 2, and is made into a state slidable in the direction of the axis center of the barrel and is housed in the barrel 1. One or more spiral grooves 7 are formed in an outer peripheral surface of the plunger 3 which slides on the barrel 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a contact probe used for electrical inspection of an inspection object such as a printed circuit board.

  For example, when conducting a continuity test of a printed circuit board, a contact probe is used to obtain electrical connection with the printed circuit board by contacting the inspection site (see, for example, Patent Documents 1 and 2).

FIG. 2 shows an example of the structure of a conventional contact probe.
As shown in the figure, this type of contact probe includes a cylindrical barrel 1 made of a copper alloy, a metal coil spring 2 built in the barrel 1, and a coil spring 2 that is biased by the barrel 1. And a plunger 3 made of carbon steel or the like accommodated in a slidable state. The distal end side of the plunger 3 protrudes from the barrel 1 to the outside by a predetermined length, and serves as a tapered contact 4 for bringing the tip of the plunger 3 into contact with the inspection location. Further, the rear end side of the plunger 3 protrudes outward from the barrel 1 and serves as a retaining portion 5 for preventing the plunger 3 from jumping out of the barrel 1 by the biasing force of the coil spring 2.

  As shown in FIG. 3, the contact probe is attached to a probe holding mechanism that is movable in a three-dimensional direction (not shown), for example, when inspecting the printed circuit board 10. Further, a lead wire 6 is connected to the zenith of the retaining portion 5 on the rear end side of the plunger 3 and connected to an inspection device (tester). The contact probe attached to the probe holding mechanism which can be moved in a three-dimensional direction is positioned so that the tip of the contact 4 comes into contact with a predetermined inspection location 11 on the printed circuit board 10 and has a predetermined stroke toward the inspection location. Pressed with. As a result, the barrel 1 moves downward by a predetermined stroke against the spring force of the coil spring 2 incorporated therein.

  The movement of the barrel 1 compresses the coil spring 2 in the barrel 1, and a downward force by the compressed coil spring 2 acts on the plunger 3. As a result, the contact 4 on the distal end side of the plunger 3 is pressed against the inspection location 11 with a predetermined contact pressure, and electrical conduction between the contact probe and the inspection location is realized, and this conduction state is stable. Maintained. In this state, necessary inspections such as a continuity test are performed by an inspection apparatus connected via the lead wires 6.

JP 2004-340597 A (all pages, all figures) JP 2004-157100 A (all pages, all figures)

  However, in the case of the conventional contact probe having the above-described structure, wear of the inner surface of the barrel progresses due to repeated sliding of the plunger 3 and the barrel 1, and a metal generated due to wear in the gap between the plunger 3 and the barrel 1. Powder accumulates. The increase in the frictional resistance due to the accumulation of the metal powder hinders the smooth sliding of the plunger 3 and causes an increase in contact pressure. In the worst case, the plunger 3 cannot be moved or an inspection object such as a printed circuit board is removed. It can also be damaged.

  The above phenomenon is particularly remarkable because when the inspection point where the contact 4 is pressed is an inclined surface, an eccentric load acts on the plunger 3 and the frictional force between the plunger 3 and the barrel 1 increases.

  The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a contact probe that does not hinder the sliding of the plunger as in the prior art even when metal powder due to wear is generated. It is.

  In order to solve the above-described problems, the present invention provides a cylindrical barrel, a coil spring built in the barrel, and a spring that is urged by the coil spring and is slidable in the barrel axial direction. In the contact probe including the plunger, one or more spiral grooves are formed on a surface of the outer peripheral surface of the plunger that slides with the barrel. The lead angle of the spiral groove may be set in the range of 10 degrees or more and less than 90 degrees according to the purpose of use of the contact probe, the object to be used, the operating conditions, and the like.

  According to the present invention, since one or more spiral grooves are formed on the surface of the plunger that slides with the barrel, even if metal powder is generated by sliding between the plunger and the barrel, the majority of the plunger is the plunger. It falls and accumulates in a spiral groove formed on the outer peripheral surface. For this reason, the metal piece generated as in the conventional case does not accumulate in the gap between the plunger and the barrel to increase the frictional resistance and prevent the plunger from sliding. A contact probe having a contact pressure can be provided.

  Hereinafter, an embodiment of a contact probe according to the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of a contact probe according to the present invention. In addition, the same code | symbol is attached | subjected to the same structure part as the conventional contact probe (FIG. 2), and the detailed description of the part is abbreviate | omitted.

  The contact probe according to the illustrated example has a structure similar to that of the conventional contact probe (FIG. 2), and has a single spiral shape with a lead angle θ = 44 degrees on the surface of the outer peripheral surface of the plunger 3 that slides with the barrel 1. The groove 7 is formed. As the groove shape, an arbitrary shape such as a semicircular groove, a V-shaped groove, or a rectangular groove can be adopted.

  When the spiral groove 7 is formed on the outer peripheral surface of the plunger 3 as described above, most of the metal powder generated by the sliding of the plunger 3 and the barrel 1 is in the spiral groove 7 formed on the outer peripheral surface of the plunger. Depressed and accumulated. For this reason, unlike the conventional case, the metal piece is not accumulated in the gap between the plunger 3 and the barrel 1 to increase the frictional resistance and prevent the plunger 3 from sliding.

(Sliding durability test)
Five contact probes (invention product) of the present invention having the structure of FIG. 1 (No. 1 to No. 5), and five conventional contact probes (conventional product) having the structure of FIG. 2 as a comparative example. (No. 1 to No. 5) were prepared, and a sliding durability test was performed on these contact probes. The results are shown in Table 1. The only difference between the product of the present invention and the conventional product is the presence or absence of the spiral groove 7 formed on the outer peripheral surface of the plunger 3, and the materials and dimensions of the components are the same.

  The test method was such that sliding at a stroke of 3 mm was repeated at a reciprocating speed of 10 times per second, and the load when the plunger 3 was pushed in by 3 mm was measured with a load cell after sliding 2 million times.

  When the sample after the test was decomposed, generation of metal powder was observed in both the product of the present invention and the conventional product. However, as is apparent from the changes in the load before and after the 2 million times durability test shown in Table 1, the conventional product shows a slight increase in load of 10% or more, but the present invention product has a slight increase. Only a slight increase in load was observed. This is because the metal powder generated by the wear of the barrel 1 accumulates in a small gap between the plunger 3 and the inner surface of the barrel 1 in the conventional product and increases the frictional resistance. As a result, the load increases. In the invention, since the metal powder fell into the spiral groove 7 formed on the outer peripheral surface of the plunger 3 and escaped, there was an amount of metal powder between the plunger 3 and the inner surface of the barrel 1 to increase the frictional resistance. This is because it was not.

  In the embodiment shown in FIG. 1, an example in which only one spiral groove 7 is formed is shown. However, if necessary, a plurality of spiral grooves 7 may be formed. And a left-handed spiral groove may be formed simultaneously. Further, the lead angle θ of the spiral groove 7 may be set in the range of 10 degrees or more and less than 90 degrees according to the purpose of use of the contact probe, the object to be used, the operating conditions, and the like. If it is less than 10 degrees, the pitch of the grooves is too small and hinders sliding, and if it is 90 degrees, it cannot be spiral.

It is sectional drawing of one Embodiment of the contact probe which concerns on this invention. It is sectional drawing which shows the example of the conventional contact probe. It is explanatory drawing of the usage method of the conventional contact probe.

Explanation of symbols

1 Barrel 2 Coil Spring 3 Plunger 4 Contact 5 Retaining Block 6 Lead Wire 7 Helical Groove θ Lead Angle

Claims (1)

  In a contact probe comprising a cylindrical barrel, a coil spring built in the barrel, and a plunger energized by the coil spring and slidable in the barrel axis direction, and accommodated in the barrel, One or more spiral grooves are formed on a surface of the outer peripheral surface of the plunger that slides on the barrel.

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